Conventionally, a discharge lamp lighting device including a load determination device is disclosed in Japanese Patent Application Laid-open No. 2001-210490. The discharge lamp lighting device is used in common to light on various kinds of discharge lamps such as a fluorescent lamp and a high-intensity discharge (HID) lamp, each having a different electrical property. In order to light on each of the discharge lamps appropriately, the discharge lamp lighting device lights on the discharge lamp with a predetermined output properties upon starting up, and then identifies a type of the discharge lamp by detecting lighting properties (e.g., voltage, current, electric power) of the lamp, i.e., determines an illumination load based on the lighting properties of the lamp.
The illumination load may include an organic electroluminescence (hereinafter referred to as “organic EL”) as well as an LED, and the lighting device is preferably common to these solid-state light emitting devices. The load determination device disclosed in the above Patent Document is adapted to determine a discharge lamp based on the properties of the discharge lamp. This technique is, however, difficult to be adapted to the determination of an organic EL and an LED because the solid-state light emitting devices have different properties from those of the discharge lamp. More specifically, in the above Patent Document, it determines a discharge lamp as the illumination load by detecting a discharge current without consideration of a capacitive component. In the case where there is an illumination load itself having a capacitance, such as an organic EL, however, the technique cannot be used as it is.